Mechanical brake for railway switch machines



H. B. TAYLOR Aug. 18, 1936.

MECHANICAL BRAKE FOR RAILWAY SWITCH MACHINES Filed Dec. 23, 1951 2Sheets-Sheet 1 Aug. 18, 1936. H. B. TAYLOR 2,051,400

MECHANICAL BRAKE FOR RAILWAY SWITCH MACHINES I Filed Dec. 23, 1951 2Sheets-Sheet 2 FIG.3.

INVENTO fin? I MM.

/A' /ATTORNEY Patented Aug. 18, 1936 UNITED STATES MECHANICAL BRAKE FORRAILWAY SWITCH MACHINES Herbert B. Taylor, Rochester, N. Y., assignor toGeneral Railway Signal Company, Rochester,

Application December 23, 1931, Serial No. 582,745

14' Claims.

This invention relates to devices used for the control of railroad trackswitches, and more particularly pertains to a mechanical brake employedwith power driven switchmachines for operating such switches.

In the operation of track switches by power driven switch machines, itis desirable that the track switch be prevented from movement at alltimes except under authorized control. The usual track switch operatingmechanism or switch machine is provided with means for positivelylooking a track switch in its extreme operated positions. However, itmay happen that the switch points are operated to the desired extremeposition, but the switch machine for one reason or another fails topositively look thetrack switch. Even in such a case, the switch machineshould be so arranged as to prevent movement of the track switch shoulda train pass thereover.

In view of the above and other considerations, the present inventionproposes to provide a mechanical brake associated with the switchmachine in such a manner, as to prevent the movement or operation of theswitch machine mechanism at all times except when power is applied toits motor. In other'words, this brake is made effective to hold theswitch points in the last position to which they. are operated,irrespectiveof whether or not the switch machine has positively lockedthe track switch in the usual manner.-

Other objects, purposes and characteristic features will be inpart'obviousirom the accompanying drawings and in part pointed out, asthe description of the invention progresses.

In describing the invention in detail, reference will be made totheaccompanying drawings, in which like reference characters indicatecorresponding parts throughout the several: views, and in which:-

Fig. 1 is a sectional view of a mechanical brake V constructed as oneembodiment of the present invention, as taken on the lines ll ofFig. 2;

Fig. 2 is a sectional view taken on lines 2--2 ofv Fig. 1;

Fig. 3 is a sectional view taken on lines 3-3 of Fig. 4; and,

Fig. 4 is similar to Fig. 1 except certain parts have beenillustrated'in their operated or released positions.

Although the mechanical brake of the present invention is contemplatedas employed with a suitable switch machine, such for example asdisclosed in the patent'to W. K..Howe, Patent No. 1,466,903, datedSeptember 4, 1923, with the .brake of the present invention interposedbetween the driving motor and the operating mechanism of the switchmachine, it is considered sufficient for an understanding of the presentinvention to know that the brake casing l is stationary with respect tothe switch machine housing, that the 5 shaft 2 is driven by the switchmachine motorin One direction or the other depending upon the operationto be accomplished, and that the pinion gear 3 suitably drives thegearing of the switch machine when the motor. rotates the shaft 2.

Also, it is to be understood thatsuitable means may be employed inconnection with a switch mae chine equipped with the brake of thepresent invention, so as to permit the hand operation of the trackswitch, but the operation of such means is unnecessary for anunderstanding of the present invention which more particularly relatesto the structure and character of the brake.

With reference to the drawings, the brake casing l isrformed so as to besecurely attached to the switch machinehousing, and is provided with aweb portion 5 which extends across the cavity within the casing (seeFigs. ,1 and 3). A plate member 6-. has a protruding shaft! whichextends through the web portion 5 forming a bearing therefor. This shaft1 is provided with a. shoulder formed thereon againstwhich the piniongear 3 is securely pressed by a suitable nut 8 (seeFig. 2). The piniongear 3-is prevented from turning on the shaft 1 by suitable keys locatedi ak w y- Another plate 9 is secured in spaced relation with the plateBso. that certain of the operating parts of the brake maybe mounted onthe inside. More specifically, four brake shoe sectors IQ. ll,

I2 and [3 are located between the plates, and pivoted at the ,fourpointsat which the plates 6 and 9 are connected together. For example, the.plates 6 and 9; are separated by-a shouldered bolt 40 I4 which isriveted at one end toplate 9 but is detachably secured by a nut IGandasuitable lock washer H to the plate 6. Thus, a bearing surface isformed by the shoulder'of the bolt M for the brake shoe sector II. theremaining brake shoe sectors I0, I2 and I3 are supported between theplates 6 and 9 at corresponding points in the remaining quadrants of thebrake.

On adjoiningportions of the brake shoe sec-. 50 tors Ill-ll and !2-.l3suitable brake linings 20, 2!, 22. and ,23 are secured for engaging; theinside. of the casing I which acts as the stationary brake drum. Theseportions ofthe brake shoesectors having the brake lining are pressed551' In a similar manner,

- 25, 2 6, 2'1 and 2s.

outwardly against the brake drum by springs The springs 25 and 26 aresupported at one end by the extending portion 30 of the plate 9; andsimilarly the springs 21' The opposite portion of each brake shoe sectoris enlarged to act'as a counter-balancing weight. Each of these weights36, 31, 38 and 39 is of such a value that the center of thecentrifugalforce acting on each brake shoe sector falls on that side ofeachsector extending from its pivot point toward the weighted orenlarged porhonor the sector. In other words, as the brake shoe "sectorsare revolved' whileithe motor is V spective brakeshoe sectors.

acting to drive the switch machine mechanism, the centrifugal'forceacting upon the brake shoe sectors is effective to counter-act to' thedesired degree the effect of the spring members of the re- The brakeshoesectors II and 2 are interconnected by a bearing joint (see 'Figs.land 3) which pro vides that movement of one sector' transmits the same'motion to the other. In

- other words, a bearingshaft wshouldered at either end fitsin-thesemi-circular recesses provided in eachof the brake shoe sectors.Similarly, a bearing shaft 4| shouldered at either end fits in thesemi-circular recesses located in the brake shoe sectors l and I3 sothat the motion-transmitted to one brake shoe sector is imparted totheother.

Each of the brake shoe sectors IO, 12 and .|3 has inwardly extendingbifurcated arms 45, 46, V

41 and 48, within which the'roller bearings 50, 52 and 53 respectively,are suitably mounted.

1 A cam'member 60 is suitably keyed to the shaft 2; and'locat'ed betweenthe plate members 6 and 9 'so'as to engage' in pairs the roller bearings50,

5|, 52 and 53 depending upon the direction in which the cam is rotated.When thecam is a from the brake drum, as illustrated in Fig. 4.

, This movement or force transmitted to the sectors rotate in aclockwise direction.

turned inaclockwise direction (see Fig. 1), the

cam;member60 engages the roller bearings 5| and 53, turning the brakeshoe sectors II and I3 in counter-clockwise directions, so as to movetheir respective brake linings 2| and 23 'away H and I3 is imparted tothe sectors I2 and M respectively through the interconnecting bearingshafts 40 and 4|, so that the sectors l2 and turnain clockwisedirections, which moves the brakelinings and 22 away from-the inside of.the brake drum. Thus, the frictional contact between the brake shoesectors and the'brake drum is released allowing the plates 6 and 9 to'The force or power imparted to the shaft 2 is now passed on to thepinion 3, inasmuch asthe brake sectors can be rotated around their pivotpoints only a limited distance which is determined by the bearings5|--52 and the bearings'50-53 V making contact. In other words, the cammember 60 is rotated with respect to theplates 6 and 9 only so long asthe brakeshoe sectors turn on their .pivo't poin'ts and when they ceaseturning and the respective pairs coincide at their bearings,gthen thecam member is stationary with respect to plates 5 and 9, but the plates6 and 9 together with the shaft 2 rotate with respect to the brake drumor casing thereby transmitting the motion of the motor armature to thepinion gear 3.

In this connection it is noted, that the shape of the cam member 60 issuch that its circular portions which engage the roller bearings 50, 5|,52 and 53 are concentric with the roller bearings when the parts are intheir operated positions (see Fig. 4). This definitely determines thelimits of the cam movement, as well as prop erly directing the forcesboth for rotational effectiveness and for releasing effectiveness. V

The operation accomplished when the cam 60 is turned in acounter-clockwise direction is similar to that already described, andwill 'be understood by analogy.

The rotation of the brake mechanism imparts centrifugal force to 'eachof the parts.

in the case of the brake shoe sectors, as previously mentioned. When themotor has reached the usual operating speed, the centrifugal forces,

thus transmitted to the brake shoe sectors. added to the releasingeffect imparted by the cam' GO due to the reaction of the load,counterbalance the force'of the springs with sufiicient margins topositively maintain-the brake released.

But when the power is withdrawn, as applied by the motor, thecentrifugal force'alone is insufficient to maintain the brakeshoes inreleased or retracted positions and they are pressed by 1 theirrespective springs against the brake. drum. This servesto stop therotation of the motor and switch machine mechanism with a minimum amountof overrun by absorbing the momentum of the parts in the frictioncreated.

- Also, it will be obvious from the above description that any forceapplied to the pinion 3 in either direction when the motor isnotactuated,

These 7 centrifugal forces are preferably balanced except will betransmitted directly through the brake shoe members to the brake drum Ithrough the frictional contact between the brake linings and the drum,thuspreventingmovement of the pin ion 3. v

The actual weight, the'degreeof balancing, the

forces, the' moments of torque, and the like are .of course consideredasengineering details and adjustment, the particular values of which arenot necessary for an understanding of the present invention.

This brake when applied to switch machines,

:as contemplated in accordancewith the present invention, willadequately prevent the movement of the track switch points due toexternally applied forces, but will allow proper operation when forcesare applied thereto through the medium of the switch machine mechanismasdriven by its'power operated motor. The brake'of, the' presentinvention also serves to limit the overrun at the end of an; operation.

Having thus shown a brake for railroad switch machines, as one specificembodiment of the present invention, it is desired to be understood ithat this form is selected to facilitate in the disclosure of theinvention rather than to limit the 7 number of 'forms which it mayassume; and, itis to befurther understood that various modifications,adaptations and alterations may be applied to the specific form showntomeet the requirements of practice, withoutin any manner departing fromthe spirit orscopeof'the present invention except as limited by theappended claims.

What I claim is:

1. For use with a power driven switch machine for railroad trackswitchesa mechanicalbrakeplurality of brake shoes for compressing saidcoil springs to disengage said brake shoes from said brake drum and forrotating said pinion. drive member withsaid power driven, shaft aftersaid brake shoes are disengaged, and means re-'v sponsive to thesynchronous, rotation of said shaft and said pinion drive member formaintainingsaid coil springs compressed.

2. For use with a power driven switchmachine for railroad trackswitches, a mechanical, brakeincluding, a fixed brake drum, a piniondrive member, a plurality of brake Shoes pivotally attached to saidpinion drive member'andnormally biased to engage said brake drum, ashaft, operating means connecting; said shaft with a plurality of brakeshoes for disengaging said brake shoes from said brake drum and forrotating said pinion drive member when power is applied to said shaft,and means effectively only while said pinion drive member is beingrotatedfor maintaining said brake shoes disengaged from said brake drum.

3. For use with a power driven switch machine for railroad trackswitches, a mechanical brake including, a fixed brake drum, a piniondrive member, a plurality of brake shoes each having an unbalancingweighton one end and'a braking surface on the other end, and each beingpivotally attached to said pinion drive member at a point between itsunbalancing' weight and its braking surface, means normally biasingsaidbrake shoes so that their respective,brakingsurfaces engage said brakedrum, a shaft, and operating means,

shoes for initially disengaging said brake shoes from said brake drumand for rotating said pinion drive member when power is applied to saidshaft, whereby the revolving of said pinion drive member and saidunbalanced brake shoes is effective to counteract said normal bias onsaid brake shoes.

4. In combination, a driven member, a driving member, a brake forpreventing operation of said driven member, means for releasing saidbrake when power is applied to said driving member, said meansoperatively connecting said driving member to said driven member whensaid brake is released, and means dependent upon the speed of operationof said driven member for maintaining said brake released duringoperation.

5. For use with a power driven switch machine for railroad trackswitches, a mechanical brake including; a fixed brake drum; mountingmeans rotatably supported with respect to said brake drum; a pinion gearattached to said mounting means; a plurality of brake shoe sectorspivotally supported on said mounting means; brake linings on each brakeshoe sector for engaging said fixed brake drum, said linings being onone side of the pivot point of each brake shoe sector; weight means onthe other side of the pivot point of each brake shoe sector; springbiasing means for normally causing said brake shoe linings to engagesaid brake drum; a power driven shaft; and operating means connectingsaid power driven shaft and said brake shoe sectors for compressing saidspring biasing means and for rotating said brake shoe sectors, saidmounting means: and said; pinion gear being in synchronism with saidpower driven shaft when, power is applied thereto; whereby said piniongear is prevented from rotation except. when power is applied tosaid'shaft; and whereby the centrifugal force acting on said unbalancedbrake shoe sectors due'to the rotation thereof is effective tocounter-act said spring biasingmeans.

6. For use with a power driven switch machine for railroad trackswitches, a mechanical brake including; a fixed brake drum; mountingmeans rotatably supported with respect to said brake drum; a pinion gearattached, to said mounting means; apluralit of brake shoe sectorspivotally supported on said mounting means; brake linings on each brakeshoe sector for engaging said fixed, brake drum, said linings being onone side of the pivot point of each brake shoe sector; weight means onthe other side of the pivot point of each brake shoe sector; springbiasingv means for normally causing said brake linings.

to engage saidbrake drum; a power driven shaft; and a cam on said shaftadapted to engage said brake shoe sectors for compressing said springbiasing means andfor rotating said brake shoe sectors, said mountingmeans and said pinion gear being in synchronism therewith when power isapplied thereto for rotation in either direction; whereby said piniongear is prevented from rotation except when power is applied to saidshaft; and whereby the centrifugal force acting on said unbalanced brakeshoe sectors due to the rotation thereof is effective to counteract saidspring biasing means.

7. For use with a. power driven switch machine for railroad trackswitches, a mechanical brake including, a fixed brake drum having acavity, two spaced plates pivotally supported within said cavity, apinion gear fixedto said plates, four:

brake shoe sectors each being pivotally supported between said plates atintermediate points near their periphery and having inwardly projectingarms, a brake lining attached to each of said brake shoe sectors on oneside of its pivot point, a weight attached to each of said brake shoesectors on the opposite side of its pivot point, coil springs associatedwith each of said brake shoe sectors for causing said brake linings toengage the inside of said brake drum, a power driven shaft pivotallysupported having the same axis as said plates, and a movement limitingcam on said power driven shaft for engaging said inwardly projectingarms, whereby said coil springs are compressed for disengaging saidbrake linings from said brake drum, whereby said plates, said brake shoesectors and said pinion are all rotated when power is applied to saidshaft, and whereby the centrifugal force acting on said weights assistsin maintaining said coil springs compressed.

8. In combination, a driven member capable of being rotated in eitherdirection, a plurality of unbalanced sectors so pivotally attached tosaid driven member that their heavier portions move outwardly when saiddriven member is rotated, biasing means for drawing the heavier portionsinwardly when said driven member is not rotated, and a friction brakedrum engaged by said unbalanced sectors when their heavier portions aredrawn inwardly by said biasing means to thereby prevent rotation of saiddriven member in either direction.

9. In combination, a driven member capable of being rotated in eitherdirection, a plurality of unbalanced sectors so pivotally attached tosaid V anced sectors when their heavier portions are drawn inwardly bysaid biasing means to thereby prevent rotation of said driven memberineither drivenmembers that their heavier portions move outwardly whensaid driven member is rotated,

biasing means for drawing the heavier portions inwardlywhen saiddrivenmember is not rotated, a'friction brake drum' engaged bysaidunbaldirection, and mechanical releasing means for counteracting saidbiasing 'means, whereby saidpendent upon the speed of rotation of said'driven member for maintainingsaid brake released. 11. In combination,'a driven member capable of being rotated, a brake for preventingrotation of said driven member, a driving member,

"means automatically releasing said brake upon the tendency of saiddriving 'member" to rotate .and then directly transmitting rotationtendency from said driving member to said driven memher; and centrifugalmeans dependent upon the speed of rotation of 'saiddriven' member foreffectively maintaining said brake'released' during 7 the rotation ofsaid driven member.

12. In combination, a driven member capable of being rotated, a drivingmember disconnected from said driven member and capable of rotation whenpower is applied thereto, a friction brake for preventing rotation ofsaid driven member in either direction, means automatically releasingsaid brake upon the application of power to'said driving member to causeit to tend to rotate,

whereby said brake is released to allow the rotation'of. said drivenmember, means directly 7 driving member.

transmitting rotational tendency from said driv ing member to saiddriven member when said brake is released, and centrifugal meansdependent' upon the speed of rotation of said driven member formaintaining said brake released by supplementing said automatic,releasing means.

13. In combinatioma driven member capable I of being rotated in at leastone direction, a friction brake for preventing rotation of said drivenmember in said one direction, a driving member,

automatic mechanical means for initially releasing said brake whendriving torque is applied to said driving member, means operativelyconnecting said driven member and said driving member for thetransference of driving: torque from said driving member to said drivenmember when said brake is released, and centrifugal means dependent uponthe speed of rotation of said driven member for effectively maintainingsaid brake released during saidrotation of said driven member. r

14. In combination, a driven shaft capable of being rotated, 'a drivingmember capable of rotation when power is applied thereto. a frictionbrake for normally preventing-rotation of said driven shaft inbothdirections while driving torque is removed .from said driving 'member,means automatically releasing said brake upon the application of drivingtorque to said driving member, whereby said brake is released to allowtransmitting torque fromsaid driving member to said driven shaft whensaidbrake is released, and centrifugal means'responsive to the speed ofrotation of said driven shaft for maintaining said 7 the rotation ofsaid driven shaft, means directly brake released by supplementing thereleasing effeet or said'automatic'releasing means, whereby torque canbe transferred from said driving mem her to said'driven shaft, butcannot be transferred from said driven shaft to said driving memberwhile driving torque is removed'fromsaid HERBERT B. TAYLOR.

